1. Field of the Invention
The present invention relates to a positive photosensitive composition which is used for the manufacture of semiconductors such as IC or the manufacture of circuit boards of a liquid crystal, a thermal head, etc. and is further used for other photofabrication steps and to a method of forming pattern using the same. More specifically, the invention relates to a positive photosensitive composition which is suitable in the case of using an irradiation source such as exposure light sources such as far ultraviolet rays of not more than 250 nm, and preferably not more than 220 nm and electron beams and to a method of forming pattern using the same.
2. Background Art
Chemical amplification type photosensitive compositions are a pattern forming material which generates an acid in an exposed area upon irradiation with active rays such as far ultraviolet rays or radiations and changes dissolution properties in a developing solution between an irradiated area and a non-irradiated area of the active rays or radiations by reaction with this acid as a catalyst to form a pattern on a substrate.
In the case of using a KrF excimer laser as an exposure light source, since a resin having, as a basic skeleton, poly(hydroxystyrene) which is low in absorption mainly in a region of 248 nm is used as the principal component, such a chemical amplification type photosensitive composition has high sensitivity and high resolution and forms a good pattern so that they are a good system as compared with related-art naphthoquinonediazide/novolak resin systems.
On the other hand, in the case of using, as an exposure light source, a light source with a shorter wavelength, for example, an ArF excimer laser (193 nm), since an aromatic group-containing compound essentially exhibits large absorption in a region of 193 nm, even the foregoing chemical amplification type photosensitive compositions were not sufficient.
For that reason, there have been developed resists for an ArF excimer laser containing a resin having an alicyclic hydrocarbon structure. For example, JP-A-2003-167347 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)) and JP-A-2003-223001 describe a composition containing a resin containing a polycyclic acid decomposable repeating unit and an acid nondecomposable repeating unit. However, in forming a fine pattern with a line width of, for example, not more than 100 nm, even if the resolution performance is excellent, there were involved a problem of pattern collapse in which the formed line pattern collapses and becomes a defect at the time of manufacturing a device and a problem of development defects by a development residue or the like at the time of development caused due to hydrophobicity of a resist polymer.
Furthermore, JP-A-2004-334156 describes a resist composition containing an acid decomposable resin containing at least two kinds of repeating units having an alicyclic hydrocarbon structure.
However, the related-art resist compositions still involve insufficient points, and further improvements regarding resolving power, isolated DOF and PFE temperature dependency.
That is, under a circumstance where the formation of a fine pattern with a line width of, for example, not more than 100 nm is necessitated, especially in forming an isolated pattern, it has become difficult to make sure of a defocus latitude (DOF), and a resist composition having a broader DOF performance is being demanded.
Moreover, in the case of using a large-sized wafer, it is already known that a scattering in the temperature in post exposure baking (PEB) by a hot plate, etc. affects the resulting pattern. Thus, an improvement of the PEB temperature dependency is being demanded.